The invention relates to a Wideband Code Division Multiple Access (WCDMA) communications systems. In particular, the invention relates to power margin management in WCDMA communications systems.
High Speed Packet Access (HSPA) is a concept within Wideband Code Division Multiple Access (WCDMA) specifications, such as Universal Mobile Communication System (UMTS), which is under the Third Generation Partnership Project (3GPP) of the European Telecommunication Standards Institute (ETSI). The main target of HSPA is to improve system capacity and throughput while reducing delay.
Within the HSPA concept, two distinct but related specifications have been standardized—High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA). HSDPA introduces new channels and features to enable high-speed packet access in the downlink direction. While connected, a user equipment (UE) periodically sends a Channel Quality Indicator (CQI) to a network node, or Node-B, indicating what downlink data rate the user equipment can support under its current radio conditions. The UE also sends an acknowledgement (Ack/Nack) for each packet such that the Node-B knows when to initiate retransmissions. With the channel quality measurements available for each user equipment in the cell, the packet scheduler may optimize its scheduling among the users.
The HSDPA concept also introduces an additional high-speed dedicated physical control channel (HS-DPCCH) in the uplink for carrying the CQI information as well as the high speed acknowledgement H-ARQ acknowledgements. Similarly, HSUPA introduces new channels and features to enable high-speed packet access in the uplink direction. Within HSUPA, two uplink dedicated channels were introduced, namely the Enhanced Dedicated Physical Data Channel (E-DPDCH) and the Enhanced Dedicated Physical Control Channel (E-DPCCH). These two channels carry the high-speed uplink packet data transmission and associated control information, respectively.